Design of high thermal expansion glass-ceramics through microstructural control

Conference · Tue Jul 01 00:00:00 EDT 1986

OSTI ID:6973581

Loehman, R E; Headley, T J

High thermal expansion glass-ceramics can be made from lithium silicate glasses that contain small amounts of P/sub 2/O/sub 5/. The essential step involves heating the glass to a temperature near 1000/sup 0/C to grow well-faceted 0.1 to 0.5 ..mu..m Li/sub 3/PO/sub 4/ crystallites in the molten glass matrix. When the temperature is lowered to the 750 to 850/sup 0/C range, a mixture of high expansion SiO/sub 2/ polymorphs and lithium silicate phases crystallize. TEM observations on one composition reveal the crystallization is by epitaxial growth on specific faces of the Li/sub 3/PO/sub 4/ crystallites. Heat treatments that do not form faceted Li/sub 3/PO/sub 4/ crystallites give glass-ceramics with much lower expansion coefficients. Our understanding and control of this epitaxial crystallization and growth mechanism has led to the development of a family of high thermal expansion glass ceramics useful for making hermetic seals with a number of stainless steels and superalloys.

• Research Organization: Sandia National Labs., Albuquerque, NM (USA)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 6973581
• Report Number(s): SAND-86-0481C; CONF-860714-7; ON: DE87003787
• Resource Relation: Conference: 22. University conference on ceramics - ceramic microstructures '86: role of interfaces, Berkeley, CA, USA, 28 Jul 1986
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
GLASS
CRYSTALLIZATION
SEALING MATERIALS
PRODUCTION
CERAMICS
EPITAXY
HEAT TREATMENTS
LITHIUM PHOSPHATES
LITHIUM SILICATES
THERMAL EXPANSION
TRANSMISSION ELECTRON MICROSCOPY
ALKALI METAL COMPOUNDS
ELECTRON MICROSCOPY
EXPANSION
LITHIUM COMPOUNDS
MATERIALS
MICROSCOPY
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PHOSPHATES
PHOSPHORUS COMPOUNDS
SILICATES
SILICON COMPOUNDS
360100* - Metals & Alloys